Your data volume might not be the same. A query might perform ok on a table with some thousands of rows but won't be ok when volume increases to millions.
That's another reason to give as much information as possible when asking for performance help.
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2